Scientists are seeking permission to carry out experiments that would result in children being born with three biological parents. UK medical authorities say they will almost certainly approve the application in the next few weeks.

The aim of the technique is to prevent mothers passing on degenerative genetic diseases to their children. But campaigners say it could lead to significant increases in elderly women having children. They also claim it represents an unacceptable step towards the creation of designer babies.

'By creating a child with three genetic parents, these scientists are taking the first step towards genetic engineering of human beings. That is not a direction in which we should be going,' said Dr David King, director of Human Genetics Alert.

The technology - which is being developed by a team at Newcastle University - will involve the implanting of the nucleus of an embryo from an affected mother into an egg taken from a donor that has been stripped of its nucleus.

Human eggs carry small spherical or rod-like bodies called mitochondria, which supply energy for the growing foetus. These have their own genes, inherited separately from the child's main chromosomal genes....................